Hygrometer



Oct. 25, 1938. D. P. WICKERSHAM ET AL HYGROMEIE R Original Filed Nov. 25, 19s

c nczuaxm INVENTOR ATTORNEYS Patented Oct. 25, 1938 UNITED STATES HYGROMETER Don P. Wickersham and Karl Otto Waldvogel,

Urbana, Ohio, assignors to The. Johnson Manufacturing Company ration of Ohio Urbana, Ohio, a corpo- Application November 25, 1935, Serial No. 51,404"

Renewed March 21, 1938 8 Claims. (or when)" This invention relates to improvements in hygrometers of the type in which the moistureresponsive element is formed of wood or similar fibrous material.

An object of the invention is to provide means for compensating for varying degrees of expansion of the"moisture-responsive element, particularly when such element is formed of wood.

In the accompanying drawing:

Fig. 1 is a front elevation.

Fig. 2 is a vertical section on the line 2--2 of Fig. 1.

Fig. 3 is a front elevation of the device with the front casing removed.

Fig. 4 is a fragmentary enlarged horizontal section on the line 4-4 of Fig. 3.

Fig. 5 is a fragmentary enlarged section on the line 55 of Fig. 2.

Fig. 6 is a view similar to Fig. 5 with the parts in a different working position.

Fig. 7 is also a view similar to, Fig. 5 with the parts in a still different working position.

Fig. 8 is a fragmentary enlarged horizontal section on the, line '8 8 of Fig. 3. Fig. 9 is a diagram illustrating the improved method of obtaining material for the hygroscopic element.

Fig. 10 is a perspective view showing a further step in the process of making the hygroscopic element. f

Fig. 11 is a chart illustrating the efiect of moisture vapor on the hygroscopic element.

Referring to the drawing, l represents a back plate on which the mechanism is mounted, the mechanism being enclosed by a front cover or casing 2. In the front casing 2 is an opening or window 3, and at 4 is shown a small section of glass supported in the casing 2. To the rearoi' the window 3 is the scale plate 5, also supported in the casing 2.. The graduations 6 on the scale plate will be explained more fullyat a later point in the description. 7

There is provided a needle 1 which sweeps over the graduations 6 on thescale plate 5. The needle I is fixed on the outer end of a sleeve'8 which is'revolubly supported on a stud 9 secured to the back plate I, the relation of the circularly disposed graduations 6 and stud 9 being concentric.

The sleeve 8 is given a partial rotation in a clock-wise direction by the actuation of the hygroscopic element l0 through linkages including a double armed lever II, a light chain [2 and a peculiarly formed lever l3 which by its formation in conjunction w t a p on 0; t e Sleeve 8 constitutes explained.

Referring to the hygroscopic element I0, this element isa member formed, in the present ina part of the invention as will be stance, of five sections of a wood such as bassment to expand in as nearly a straight line as possible. v p

This is explained. as follows: 'Woo'd reactsto absorbed moisture by expanding in all directions; that is, a stick of wood will increase in length, breadth and thickness. Its greatest degree of increase, however, is in a direction along the lines of the originaltree annulations 'or tree growth'rings, and advantage is taken ofthis property in making the improved element by so selecting the lumber of which the element is formed that the annulationsor: growth-rings are substantially in alignment from end to end of the'element.

This selection of material is made by taking from the lumber sawed from a logonly a few of the boards removed from the outer periphery of the log. Referring to Fig. 9, the log is represented at M and the annulations thereof at [5. As can be seen, the saw-cuts l6 by'which the first boards are taken from the log as shown on the three sides illustrated are tangential to the annulations l4, and in distinguishing the broader surfaces of a board as the top and bottom surfaces, it will be'seen that. somefew annulations extend from edge to edge andjare substantially parallel to the top and bottom surfaces, and if the log is comparatively large in diameter there is little noticeable lack of parallelism in these firstboards. v} f As was stated, the greatest degree of expansion or increase inthe dimensions of the board is in the direction of the annulations," therefore, in such boards as are mentioned it is the width that shows the greatest increase. Accordingly, these are the preferred boards, those which would be out later toward the center having annulations of .too short radius. I

In expanding, the preferred boards, even of comparatively large radius, tend to bo'w to an arcuate formdue to theannulations, and to cause 7 taken up. in the end. grain, and nine end? A, B, C, D and E are taken from lumber pro e;

cured by the selective process just described f 1;0 five different trees of the same species.

direction, as strips A, C and E show annulations bowing generally and slightly upward, ,whi le.' strips B and D, the curves are generally ward, and that all the annulations are in a general alignment from edge to edge of the plank 1 These. strips. are. cemented to, each. other b a water-proof cement in forming this laminated plank.

The hy roscopi elemen s. lflgarel utifr mfithe endof the laminated plank, thesawcutsby' which they are. removed being indicated atf'la, Flg. "1 0., and the dimension, that was, the widthf of the plank is. now the length. of the; detachedfele ment.v Also, the annulationsiare n sli s ari isily i t ali mnexitfr m en 'to en i theel nie it as can be. seen; in the elementiilll, l'gig z; although it should. be understood hot in a h instance v annulations are shown curved to a agee ated r e for the. purposes oie iila'nin em od. of man iac urinej'. the lemeht i It is preferable tha'tth' elements"'s comparatively thin, referring tqtheleng t v end rain; in absorbing moisturegmu hrof it is is. short, as is. shown'fin the present. case inFi gs,

and a for theelement in; theimne eq reem ies'ponding ma change" i thefatinospheref'is' shortened, either from adryer to a'rnore stateoi: vice versa. '1 f.

In manufacturing a. wooden element afterfthe manner described, warping or buckling is 'elimi hated and a timelag; is provided peculiarity ofthe wooden element tione and at a. later portion of th. a. description is givenoi'the me ns .orcom pensating for thispeculiarity. f f1 f If: f

The. mountin of the. element It on .theffback plate 2 consists of a metallic-strip riveted rivets 2| to the 'backplatefle At the upperfland lower ends. of the strip. 20 the .end'port'ions are outwardly turned (Figs. 2, and'3lto 'for'm parallel arms 22 and 23]. Thr u h a gn openings in. the arms 22 and 23 two parallel Yrods 24ers passed... 'I' e e ro s are. guides for the e ment 10., as in the edge s of; the elementj lflfare lengthi wise. grooves 25 slightlylarger-thanjthe'rods 24. These grooves are. cl arlyindicatedih he snlarged sectional view Fi hand-are also'shown in the end element in Fig; 10 in broken: nes. Incidentally, thegrooves 2.5 serve toprovide very short end rain. atth s port ons of hee emeht- The. wooden element rests on arr-adjustably fixed pl 6 (Fi 2 andh) sIidahlywi posQ in relation to the-guide. rods-and supported on a sm l t s r hread hith i 13.- The purpose of this adjustmentqwill also appear lat-en H I, v

Any p ns on or con r c o the e em du ts-atm s heric humidity ha ges i communi o e to the 1 by the Previously men:

It shoul also be explained that in assembling this nated plank P that it is essential; thatthe apnua i lations of alternate strips curve inither The other longer arm H" of this lever ll consists of a sheet metal member Ila having a sheave-like groove formed in its outer edge which is concentrie; to the stud 28 on which the lever Male pivoted, At the lower end of the groove 30 axerwlight-chain I2, here shown considerably exaggerated as tosize, is connected, a chain being ....preferred because, being of a material not susceptible to. humidity changes, only the changing 'of the element itself is communicated to the needl'e-.= The upper end of the chain I2 is connes ed to, the l v r 3 se ured to previously mentioned sleeve. it to. w i h th ed e 1 is attached, f f

' As before stated, the lever 13 is peculiarly tonnedin rd r to, com ens pe ri y in, the manner in which the wooden element eypandsfon absorption of moisture, the peculiarity being that an, increase is: slight up, to. a con-. dition re resented. by a figure such 65% relative humidity, but thereafter tothehighest figure the in re se is m ch. greater-1' ul ty is illustrated by the graph shown in Fig. 11. Refer? ring, to. this i u expans o s plotted a i percentages of relative humidity, whereby the rate f. expansi n i sh wn. Astot curve indicated at 3|, this curve has anindefinite origin near th n int p sented y .0% lative nid y since little is known of. conditions belowthis per enta e and h a a ei i e n in e the 100% relative humidity portion, as this con-. dition seldomoccurs, but it will be noticed that from the .origin to. approximately 65% relative h unidityi hetu 've 3.! is fa r y un to m i its rise. 'Fr0m"65'%f to, approximately relative hum dity th riseiis m c mor .v a r p d t Pro... ooo r s duo -eh nees h mi ity cam diti'ons is'shown by the dimensions E and E. on the expansion. side f the char th r b owi thatfthejris' E for a change oi from 65% to 95% relative humidity (30% only) is nearly twice the rise .E ,fro! n, 10%, to 65%, which represents an ase? 0i; 55% nearly twi ein r eso 9%. just. mentioned.

fflfl is. means'tha mpe sat g devices were notv employed t era u tions, 6 on. the s a e plate 5 could not be equally spaced as is, preferred for ea y readi g. it b in no ic d t a t g dualtions '5 of. the present. invention extend overa hali'circlje' and a d de i t e equa sp e the indicia 0, to, 100. being read in percentages of re ativ umi ty- Thelever I3 is secured to the rear end of the sleeveand. the c ain. 12 s ho d t its out or r e end, thechaint os ov o the i h (Fig. 3 )v irom'its connection on the left to the lever H nd pa i to e gh o e pivotal enter of, the .ne clle as represented by he it. T er fore b es ex nsion of th l ment ID the increase in length results in an up: ard m emen f th horte a m' I l, a downwardmovement oi the longenarm II" and a. downwar pull on the ha n 2 wh h aus s partial rotation; of the, needle to the right transmitt hsa expan ion in length of the element from a low figure to approximately on the scale, which represents, as stated. before, a small'increasein the length of the element for a considerable change in atmospheric-conditions it is necessary to provide, in effect, that the radius at which the upper end of the chain is 'connected to the sleeve 8 should be proportionately small as compared to the longer lever arm I l This is accomplished in the'present invention by causing the run of the chain to bear against a portion of the sleeve 8 which is machined at this point to provide the suitable radius. This portion of the sleeve 8 is the groove 32 (Figs. 2

and 4) and the depth of the groove is such that the chain makes contact with sides of the groove at the proper radius.

This feature is partially shown in Fig. 5, wherein it can be seen that if the lever l3 were to be moved from-the left to its present vertical position that, regardless of the point or radius at which the chain i2 is actually connected to the lever 13, the effect is similar to a chain and sprocket system, the movement of the needle being uniformly proportional to the increase in length of the element l0 so long as the run of the chain bears against the bottom of the groove 32.

A further increase in atmospheric humidity causes the element to increase in length at a more rapid rate and to slow down the needle movement it is necessary to provide an effect similar to placing the chain on a sprocket oflarger diameter. This is provided for by so placing a finger 33 extending outwardly from the right edge of the lever l3 that the run of the chain in bearing against the finger is the same as described in connection with the groove 32; that is, when the chain leaves the groove 32 or the radius represented thereby, and so long as the chain bears against the finger, up to the point where it leaves the finger (Fig. 6), the needle movement is over a shorter range. This range on the scale extends from approximately 60% to 75% relative humidity.

For percentages above the latter figure, the needle must be still further slowed down which is done by passing the chain over the bentover extreme outer free end I 3' of the lever 13. It should also be explained that no error is introduced byan unsuitable method of connecting the lower end of the chain to the lever I I. As before stated, there is provided a plate Ila attached to the lever II, forming the longer lever arm H. The partial periphery of the plate Ila is grooved, the groove being concentrically disposed with reference to the stud 28. In this groove the run of the chain lies, the

chain being connected to the plate at the lower end of the groove. Thus, the chain is tangent to the axis of rotation of the lever H and the effective radius does not change, and the proportions of this radius with the effective radii as represented by the contact of the chain with the groove 32, the finger 33 or the free end iii of the lever l3 do not change.

When the degree of humidity decreases, the element If! gives up its moisture and contracts and becomes shorter. The lever H follows this decrease in length due to the effect of the return spring 34 which is hooked at one end to any suitable point on the back plate 2 and also by chain 35 to any suitable point on the lever l3, the chain passing to the left of the center of the needle. Consequently, as the element shrinks, the needle moves to the left.

In assembling the hygrometers, it is preferable that the elements are of the same approximate length at the'same'pproximatepercentage of relative humidity. Accordingly, the plank P (Fig. 10) is slightly wider, and thereby provides slightly longer elements than are needed for any condition of humidity. The elements are then subjected to acontrolled humidity condition for a suitable time to insure that they are stationary at that condition, and are then trimmed to a definite length. This means that each time that length isreached, the conditions are the same as the controlled condition. To compensate for any small error in controlling the humidity condition or in trimming the element to length, the small set screw 2? previously mentioned is ru up or down, as the case may be.

Having thus described our invention, we claim:

1. In a hygrometer, a moisture-responsive element, a lever operated thereby, an oscillatory sleeve, a pointer carried by said sleeve, a second lever connected with said sleeve, a chain connecting said levers, said chain bearing on said sleeve during a predetermined movement of said pointer from zero to impart a uniform movement to said pointer, said chain thereafter being free from said sleeve, and means on said second lever to cause a slower movement to be imparted to said pointer.

2. In a hygrometer, a moisture-responsive element, a lever operated thereby, an oscillatory member, a pointer carried by saidmember, a second lever connected with said member, a chain connecting said levers, said chain during a given initial movement of said moisture responsive element passing over a surface on said oscillatory member of given radius with relation to the axis of oscillation of said oscillatory member and during subsequent movement of said moisture-responsive element passing over surfaces on said second lever of increasing effective radii with respect to the axis of oscillation of said member.

3. In a hygrometer, a moisture-responsive element, a lever operatedthereby, and an oscillatory member, a second lever connected to said member, a chain connecting said levers, said chain during a given initial movement of said moisture-responsive element passing over a surface on said oscillatory member of given effective radius with relation to the axis of oscillation of said oscillatory member, and a projection on said second lever of greater radius with relation to the axis of oscillation of said oscillatory member over which said chain passes after leaving said surface during the subsequent movement of said moisture-responsive element to decrease the speed of movement of said pointer.

4. In a hygrometer, a moisture-responsive element, a lever operated thereby, and an oscillatory member, a second lever connected to said member, a chain connecting said levers, said chain during a given initial movement of said moisture-responsive element passing over a surface on said oscillatory member of given radius with relation to the axis of oscillation of said oscillatory member, and a projection on said second lever of greater effective radius with rela tion to the axis of oscillation of said oscillatory member over which said chain passes after leaving said surface during the subsequent movement of said moisture-responsive element to decrease the speed of movement of said pointer, said second lever having a surface of greater eifective radius with respect to the axis of oscillation of said oscillatory member than that of said projection over which said chain passes after speed of movementof said pointer.

- 5. In a hygrometer, a moisture-responsive element, a lever operated thereby, an oscillatory member, a pointer carried by said member, a second lever connected to said member, a chain connecting said levers, means on said oscillatory member and cooperating with said chain for causing said pointer to move at a substantially constant speed during a predetermined initial expansion of said moisture-responsive element, and means on said second lever and cooperating with said chain and acting during the subsequent expansion of said moisture-responsive element to decrease the rate of movement of said pointer. I

6. In a hygrometer, a moisture-responsive element, a lever having a short arm operatively associated with said element and a long arm having a sheave-like groove concentric with the axis of rotation of said lever, an oscillatory member, a second lever connected with said member, a chain connecting said levers and located in said concentric groove, a pointer carried by said oscillatory member and .means on said oscillatory member, a pointer carried by said member, a. second lever connected to said member, a chain connecting said levers, means on said oscillatory member and cooperating with said chain for causing said pointer to move at a substantially constant speed during a predetermined initial expansion of said moisture-responsive element, means on said second lever and cooperating with said chain and acting during the subsequent expansion of said moisture-responsive element to decrease the rate of movement of said pointer, and a spring to return the parts when the moisture-responsive element contracts.

8. In a hygrometer, a moisture-responsive element, a lever having a short arm operatively associated with said element and a long arm having a sheave-like groove concentric with the axis of rotation of said lever, an oscillatory member, a second lever connected with said member, a chain connecting said levers and located in said concentric groove, a pointer carried by said oscillatory member, means on said oscillatory member acting upon said chain to cause said pointer to move at a substantially constant speed during a predetermined initial expansion of said moisture-responsive element, means on said lever acting during a subsequent expansion or said moisture-responsive element to decrease the rate of movement of said pointer, and a spring to return the parts when the moisture-responsive element contracts.

DON P. WICKERSHAM. KARL OTTO WALDVOGEL. 

